WASHINGTON — The Obama administration yesterday dismissed calls by Republicans to halt its $700,000, tax-funded Andy Griffith ad campaign aimed at lifting dismal public approval of health-care reform, even as an independent group trashed the veracity of the TV spot.

“The ad is part of our annual effort to inform Medicare beneficiaries about changes to Medicare,” said Peter Ashkenaz, spokesman for the Centers for Medicare and Medicaid Services.

He said CMS picked actor Andy Griffith for the nationwide ad because he “is one of the most popular and trusted voices with seniors.”

Griffith was not paid for his performance, he said.

But Republicans say the ad campaign goes well beyond general explanations of Medicare benefits, and argues in favor of the health-care law, whose repeal is favored by 59 percent of voters, according to a poll.

The campaign’s “promise that ‘benefits will remain the same’ is just as fictional as the town of Mayberry,” wrote Brooks Jackson of FactCheck.org.